Pressure Testing Feedwater Heaters and Power Plant Auxiliary Heat Exchangers

2010 ◽  
Author(s):  
Stanley Yokell
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
Heat Exchangers ◽  
Wire Drawing ◽  
Pressure Vessels ◽  
Shell Side ◽  
Auxiliary Equipment ◽  
National Board ◽  
Pressure Testing ◽  
Test Pressure

This paper discusses factory and field pressure testing of tubular heat transfer equipment such as closed feedwater heaters, steam surface condensers and power plant auxiliary heat exchangers built to Section VIII Division 1 of the ASME Boiler and Pressure Vessel Code (the ASME Code) and repaired or altered in accordance with the National Board Inspection Code (NBIC). It discusses the ASME Code’s and the NBIC’s requirements for hydrostatically testing unfired pressure vessels which includes tubular heat transfer equipment. It points out that using pressure gage indications of pressure loss to determine if there is a leak from the tube side to the shell side when the back face of the tubesheet is not visible does not reveal very small leaks or weeping. For the purposes of this paper, we define weeping, VRRLeak, as a leak of 20 drops per hour or approximately 1 cm3 [0.061 in3]. During typical half-hour hydrostatic test pressure holding periods, such weeping would amount to 10 drops of water on the tubesheet face or 0.5 cm3 [0.0305 in3]. Weeping through tube-to-tubesheet joints of high-pressure feedwater heaters can lead to wire drawing (wormholing), which can materially reduce the heater life. Leaks from the channel to the shell side of steam surface condensers and auxiliary condensers can introduce brackish water into the condensate. Depending upon the fluid flowing in the tubes, contaminants can enter the shell side of other auxiliary equipment when the channel pressure is higher than that of the shell. The paper concludes that Users must advise Designers and Manufacturers of the hazards of small leaks through the tube-to-tubesheet joints. It recommends that these three entities must agree on suitable leak tests.

Pressure Testing Feedwater Heaters and Power Plant Auxiliary Heat Exchangers

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Stanley Yokell
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
Pressure Vessel ◽  
Heat Exchangers ◽  
Pressure Gauge ◽  
Pressure Vessels ◽  
Shell Side ◽  
Auxiliary Equipment ◽  
National Board ◽  
Pressure Testing

This paper discusses factory and field pressure testing of tubular heat transfer equipment such as closed feedwater heaters, steam surface condensers, and power plant auxiliary heat exchangers built in accordance with Section VIII, Division 1 of the ASME Boiler and Pressure Vessel Code (the ASME Code) and repaired or altered in accordance with the National Board Inspection Code (NBIC) (The ASME issues the ASME Boiler and Pressure Vessel Code at three-year intervals and issues Addenda annually; The National Board Inspection Code (NBIC), 2007 edition (three volumes), ANSI/NBBPVI NB23-2007, The National Board of Boiler and Pressure Vessel Inspectors, Cleveland, OH). It discusses the ASME Code’s and the NBIC’s requirements for hydrostatically testing unfired pressure vessels, which include tubular heat transfer equipment. It shows by analysis that using pressure gauge indications of pressure loss to determine if there is a leak from the tube side to the shell side when the back face of the tubesheet is not visible does not reveal very small leaks or weeping. For the purposes of this paper, we define weeping, Vleak, as a leak of 20 drops/h or approximately 1 cm3/h(0.061 in.3/h). During typical half-hour hydrostatic test pressure-holding periods, such weeping would amount to 10 drops of water on the tubesheet face or 0.5 cm3(0.0305 in.3). Weeping through tube-to-tubesheet joints of high pressure feedwater heaters can lead to wire drawing (wormholing), which can materially reduce the heater life. Leaks from the channel to the shell side of steam surface condensers and auxiliary condensers can introduce brackish water into the condensate. Depending upon the fluid flowing in the tubes, contaminants can enter the shell side of other auxiliary equipment when the channel pressure is higher than that of the shell. This paper concludes that users must advise designers and manufacturers of the hazards of small leaks through the tube-to-tubesheet joints. It recommends that these three entities must agree on suitable leak tests.

scholarly journals Performance Analysis and Design Optimization of Shell and Tube Heat Exchangers

2021 ◽  
Author(s):  
praveen math
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Pressure Loss ◽  
Fluid Flows ◽  
Hot Water ◽  
Flow Conditions ◽  
Shell Side ◽  
Shell And Tube ◽  
Side Flow

Abstract Shell and Tube heat exchangers are having special importance in boilers, oil coolers, condensers, pre-heaters. They are also widely used in process applications as well as the refrigeration and air conditioning industry. The robustness and medium weighted shape of Shell and Tube heat exchangers make them well suited for high pressure operations. The aim of this study is to experiment, validate and to provide design suggestion to optimize the shell and tube heat exchanger (STHE). The heat exchanger is made of acrylic material with 2 baffles and 7 tubes made of stainless steel. Hot fluid flows inside the tube and cold fluid flows over the tube in the shell. 4 K-type thermocouples were used to read the hot and cold fluids inlet and outlet temperatures. Experiments were carried out for various combinations of hot and cold water flow rates with different hot water inlet temperatures. The flow conditions are limited to the lab size model of the experimental setup. A commercial CFD code was used to study the thermal and hydraulic flow field inside the shell and tubes. CFD methodology is developed to appropriately represent the flow physics and the procedure is validated with the experimental results. Turbulent flow in tube side is observed for all flow conditions, while the shell side has laminar flow except for extreme hot water temperatures. Hence transition k-kl-omega model was used to predict the flow better for transition cases. Realizable k- epsilon model with non-equilibrium wall function was used for turbulent cases. Temperature and velocity profiles are examined in detail and observed that the flow remains almost uniform to the tubes thus limiting heat transfer. Approximately 2/3 rd of the shell side flow does not surround the tubes due to biased flow contributing to reduced overall heat transfer and increased pressure loss. On the basis of these findings an attempt has been made to enhance the heat transfer by inducing turbulence in the shel l side flow. The two baffles were rotated in opposite direction to each other to achieve more circulation in the shell side flow and provide more contact with tube surface. Various positions of the baffles were simulated and studied using CFD analysis and th e results are summarized with respect to heat transfer and pressure loss.

Performance Study of Heat Exchangers with Continuous Helical Baffles on Different Inclination Angles

2013 ◽  
Vol 655-657 ◽  
pp. 461-464 ◽  
Author(s):  
Su Fang Song
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Performance Study ◽  
Three Dimensional Model ◽  
Shell Side ◽  
Inclination Angles

The three-dimensional model of heat exchangers with continuous helical baffles was built. The fluid flow dynamics and heat transfer of shell side in the helical baffled heat exchanger were simulated and calculated. The velocity, pressure and temperature distributions were achieved. The simulation shows that with the same baffle pitch, shell-side heat transfer coefficient increased by 25% and the pressure drop decreases by 18% in helical baffled heat exchanger compared with segmental helical baffles. With the analyzing of the flow and heat transfer in heat exchanger in 5 different inclination angles from 11°to 21°, it can be found that both shell side heat transfer coefficient and pressure drop will reduce respectively by 86% and 52% with the increases 11°to 21°of the inclination angles. Numerical simulation provided reliable theoretical reference for further engineering research of heat exchanger with helical baffles.

Comparative Experimental Study on Performance of Corrugated Tube and Straight Tube Heat Exchanger

2012 ◽  
Vol 560-561 ◽  
pp. 156-160
Author(s):  
Lin Ping Lu ◽  
Liang Ying
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Straight Tube ◽  
Lower Stress ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Corrugated Tube

The experiments on heat transfer coefficient, pressure drop and thermal stress were done to heat exchangers with corrugated tubes and staight tubes. By analyising and comparing the heat transfer coeffient, pressure drop in tube side and shell side and axial force and stress, some conclusions can be conducted that the corrugated tube heat exchanger has better heat transfer coeffient, higher pressure drop and much lower stress caused by temperatur difference, also, it has obvious advantages under the circumstance of low Reynolds number and high temperature difference.

Shell Side Flow and Heat Transfer Performances of Trisection Helical Baffle Heat Exchangers

2013 ◽  
Author(s):  
Yaping Chen ◽  
Cong Dong ◽  
Jiafeng Wu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Incline Angle ◽  
Shell Side ◽  
Single Vortex ◽  
Flow And Heat Transfer ◽  
Helical Baffle ◽  
Side Flow

The flow and heat transfer performances of three trisection helical baffle heat exchangers with different baffle shapes and assembly configurations, and a continuous helical baffle scheme with approximate spiral pitch were numerically simulated. The four schemes are two trisection helical baffle schemes of baffle incline angle of 20° with a circumferential overlap baffle scheme (20°TCO) and a end-to-end helical baffle scheme (20°TEE), a trisection mid-overlap helical baffle scheme with baffle incline angle of 36.2° (36.2°TMO), and a continuous helical baffle scheme with baffle helix angle of 16.8° (18.4°CH). The pressure or velocity nephograms with superimposed velocity vectors for meridian slice M1, transverse slices f and f1, and unfolded concentric hexagonal slices H2 and H3 are presented. The Dean vortex secondary flow field, which is one of the key mechanisms of enhancing heat transfer in heat exchangers, is clearly depicted showing a single vortex is formed in each baffle pitch cycle. The leakage patterns are demonstrated clearly on the unfolded concentric hexagonal slices. The results show that the 20°TCO and 18.4°CH schemes rank the first and second in shell-side heat transfer coefficient and comprehensive indexes ho/Δpo and ho/Δpo1/3. The 20°TEE scheme without circumferential overlap is considerably inferior to the 20°TCO scheme. The 36.2°TMO scheme is the worst in both shell-side heat transfer coefficient and comprehensive index ho/Δpo1/3.

Semi-Analytical Calculation of the Inlet Zone Performance of Ideal Shell and Tube Heat Exchangers

2010 ◽  
Author(s):  
K. Mohammadi ◽  
W. Heidemann ◽  
H. Mu¨ller-Steinhagen
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Numerical Data ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Performance Factor ◽  
Shell And Tube ◽  
Inlet Zone

A semi-analytical model is presented for the evaluation of the performance factor of the inlet zone of an E type shell and tube heat exchanger without leakage flows. The performance factor is defined as the ratio of dimensionless heat transfer coefficients and pressure drops of both vertical and horizontal baffle orientation and therefore facilitates the decision between horizontal and vertical baffle orientation of shell and tube heat exchangers. The model allows the calculation of the performance factor of the inlet zone as a function of the baffle cut, the shell-side Reynolds number at the inlet nozzle and the Prandtl number of the shell-side fluid. The application of the model requires the knowledge of the performance factor of water at baffle cut equal to 24% of the shell inside diameter. For the development of the model a numerical data basis is used due to the lack of experimental data for shell and tube heat exchangers with different baffle orientations. The numerical data are obtained from CFD calculations for steady state conditions within a segmentally baffled shell and tube heat exchanger following the TEMA standards. Air, water and engine oil with Prandtl numbers in the range of 0.7 to 206 are used as shell-side fluids. The semi-analytical model introduced for the performance factor predicts the CFD results with a relative absolute error less than 5%. The presented model has to be validated with further experimental data and/or numerical results which explain the effect of baffle orientation on the shell-side heat transfer coefficient and pressure drop in order to check the general applicability.

Sign in / Sign up

Export Citation Format

Share Document